Luciana Gomes Barbosa

Periphytic algae dynamics in lentic ecosystems in the Brazilian semiarid

The hydrological periods drive the structure and organization of aquatic communities in semiarid regions. We hypothesize that a decrease of the precipitation during the dry period will favor the development of the periphytic algal community, leading to higher richness and density in this period. To test this hypothesis, we investigated the changes in the periphytic algal community structure in three shallow and eutrophic ecosystems of the Brazilian semiarid. The sampling was performed between 2007 and 2010 at two-mensal intervals. The sampling of periphytic algal was performed in aquatic macrophytes and rocks. The abiotic variables were analyzed simultaneously. Dominance in diatoms, cyanobacteria and chlorophytes, respectively, was observed in two periods. In the dry period, waters were alkaline and had high concentrations of nitrate and total phosphorus associated with the highest densities of Bacillariophyceae. In the rainy period the water was warmer, oxygenated and high concentrations of ammonia and soluble reactive phosphorus with diatoms remained dominant but with reduced density, while cyanobacteria and chlorophytes increased. Overall, periphytic algal community composition no responded to changes in the hydrological periods. However, the hydrological periods altered the dynamics of periphytic algal community, supported by the alternation of the most representative classes (diatoms and cyanobacteria) between the hydrologic periods. Our data suggest that the morphometric and chemical and physical characteristics of lentic aquatic ecosystems studied were more important in the dynamics of periphytic algal community than the hydrological periods and types of substrates.

Grupos funcionais em mesoambientes com piscicultura: efeitos da eutrofização artificial na dinâmica e estrutura funcional do fitoplâncton

O presente estudo objetiva identificar os grupos funcionais e as especies descritoras presentes em mesocosmos com piscicultura. O estudo foi realizado no periodo de janeiro a maio de 2010, com amostragens realizadas em intervalos quinzenais na subsuperficie. As variaveis abioticas obtidas foram: temperatura, transparencia da agua, zona eufotica, condutividade eletrica, oxigenio dissolvido, pH, n-amoniacal, nitrato, nitrito, fosforo total, fosforo reativo soluvel. Os grupos funcionais foram agrupadas com base nas caracteristicas ecologicas/adaptativas. Os resultados demonstram que as condicoes ambientais presente nos mesocosmos favoreceram principalmente especies R-estrategistas, que apresentam elevado MDL e adaptacao as condicoes ambientais de corpos aquaticos do semiarido, dado seus baixos requerimentos de luz e por serem aptas a explorarem ambientes com aguas misturadas. Os grupos funcionais refletiram as mudancas experimentadas pela comunidade algal, fornecendo importantes informacoes sobre a ecologia dos ambientes, sendo notoria a presenca de grupos tipicos de lagos rasos eutroficos.